Chemical pulping process



Patented Nov. 21, 1933 UNITED STATES (PATENT 1,935,728 FICE 1,935,728 v CHEMICAL PULPING PROCESS of Maine No Drawing. Application October 27, 1931, Serial No. 571,462. Renewed April 14, 1933 Claims.

This invention relates to the pulping of raw cellulosic materials, more especially of the nature of manila, sisal, ramie, and similar best or leaf 5 fibrous sources.

The use of solutions of sodium sulphite in the pulping of raw cellulosic materials has long been known, but I have found that such a solution can be applied to best advantage when it is supplemented by the use of other reagents in the pulping of raw cellulosic materials like manila, sisal, and ramie. Thus, I have found that if such raw cellulosic material is first treated with chloiine water and/or hyprochlorite liquor (e. g., sodium or calcium hypochlorite liquor), and, if desired, washed, it is then possible to effect pulping without the application of much heat in dilute sodium sulphite solutions to produce a pulp possessed both of excellent physical characteristics and easy bleachability. This sort of practice is not advantageous, so far as I am aware, in the case of wood,

for the treatment of raw wood with chlorine and or hypochlorite is not attended by subsequent ease of pulping in a sodium sulphite solution.

Specifically, the procedure of the present in vention may be practiced somewhat as follows.

The raw manila fiber or the like may be steeped in chlorine water containing, say, about 5% to 8% chlorine, based on the weight of dry fiber. After the chlorine has been practically consumed, for which purpose a thirty-minute period is ample, the material is preferably washed free of residual chlorine and reaction products. The washed material is then digested at about 300 to 335 F.

3 in a plain solution of sodium sulphite, which need 5 not be of greater than about 2% strength. After a cooking period of about three hours, the ma terial has been resolved into a pulp characterized by its excellent strength and other physical characteristics. The pulp is then washed free of cooking liquor and may be brought to whiteness with a bleaching liquor containing as little as 2% to 3% calcium hypochlorite, based on the weight of dry pulp.

The merit of my process lies in the fact that I can use sodium sulphite solutions of such low strength that the spent liquor resulting from the cooking operation can be discarded and yet en able commercial practice of my process. Again, the cooking can be performed at temperatures even as low as 212 F. and yet conduce to a satisfactory pulp, when suillcient chlorine, say, from 6% to 12% based on dry raw material, is used in the pretreatment. The cooking liquor should be one containing sodium sulphite as the essen-' tial and predominating fiber-liberating agent, although it can advantageously also contain sodium carbonate and/or sodium sulphide in substantial amounts. I do not, however, herein as the fiber-liberating agents, as this is described and claimed in my application Serial No. 571,461, filed October 27, 1931'.

The process of the present invention extends .to waste fibrous materials, such as old rope, twine, bagging, or the like, in which raw manila, sisal, ramie, or the like has been employed. Such waste materials are likely to contain oil, dirt, or other foreign ingredients, which can best be removed by boiling in soapy water or other cleansing or emulsifying liquors before the chlorinating treatment and the cook of the present invention are applied.

In view of the fact that both chlorine water and hypochlorite liquors are oxidants, I shall refer generically in the appended claims to the use of either or both these reagents or their equivalents as an oxidizing treatment.

What I claim is:

1. A process which comprises treating raw fibrous material of the character of manila, sisal, and ramie with an oxidizing reagent of the nature of chlorine water and hypochlorite liquor, and then pulping the material in a liquor containing sodium sulphite as the essential fiber-liberating agent.

2. A process which comprises steeping raw fibrous material of the character of manila, sisal, and ramie in chlorine water, washing, and then pulping in a solution containing not more than about 2% sodium sulphite as the essential fiberliberating agent.

3. A process which comprises chlorinating raw fibrous material of the character of manila, sisal, and ramie, and then pulping the chlorinated material at a temperature not exceeding about 335 F. in a solution containing sodium sulphite as the essential fiber-liberating agent.

4. A process which comprises treating raw fibrous material of the character of manila, sisal, and ramie with an oxidizing reagent of the nature of chlorine water and hypochlorite liquor, and then digesting the chlorinated material in a liquor containing sodium sulphite and sodium sulphide as' the essential fiber-liberating chemicals.

5. A process which comprises treating raw fibrous material of the character of manila, sisal, and ramie with an oxidizing reagent of the nature of chlorine water and hypochlorite liquor, and then digesting the chlorinated material in a liquor containing sodium sulphite and sodium sulphide as the essential fiber-liberating chemicals, the sodium sulphite being present in said liquor in preponderating amount but not exceeding about 2%.

GEORGE A. RICHTER.

claim the use of a pulping liquor made up essentially of sodium carbonate and sodium sulphide 

